Nine hospitalised as NSW temps hit 42C

PARAMEDICS have treated more than a dozen people for heat exhaustion, as temperatures soared to almost 43C in parts of the state.

Across NSW nine people were hospitalised on Saturday, suffering heat stroke, stress or heat exhaustion, while another three were treated by ambulance staff.

At Bondi in Sydney's east, a 91-year-old man was taken to St Vincent's Hospital in a stable condition, while in Raby in the southwestern suburbs, a 19-year-old man was hit with heat stroke while playing cricket and taken to Campbelltown Hospital.

The incidents came after Sydney ushered in its hottest start to summer overnight since records started in 1859.

The Bureau of Meteorology (BoM) said the city experienced a minimum of 23C overnight.

"It was a first night of summer record," meteorologist Julie Evans told AAP.

Meanwhile, on Saturday the hottest place in the state was Coonamble in NSW's central west, which reached 42.8C, the bureau said.

In western Sydney, temperatures did not hit the maximum of 40C forecast, instead peaking at about 38C.

"That was because we did have more cloud around than was expected," Ms Evans said.

Cooler weather is expected for Sunday, with scattered showers and a minimum of 21C and a maximum of 24C forecast for Sydney.

In Penrith, a maximum of 26C is expected, while people in Moree in northern NSW will face the state's highest temperature at 41C.

Ms Evans said despite the drop in temperatures, humidity is expected to linger across Sydney until mid-week.

"On Wednesday, a westerly change is coming through and taking a lot of that humidity away."

However, she said, early forecasts show that next weekend could bring high temperatures back across the state, with a top of 31C forecast for Sydney next Saturday and a maximum of 37C in the western suburbs.

"What we are seeing for next weekend is similar to what we are having today, which is mid to high 30s."

She said it was shaping up to be a warmer summer than last year.

"Last summer, only two days reached 30C at Observatory Hill (in Sydney)."